green, often with a reddish tinge, older parts of the stem: leaves > internodes, upper part of the stem arising obove the surface of the water (up to 10-15 (35) cm).

Fruit and seeds

Description of seed:

each mericarp beaked and with outer face 2-ridged and minutely papillose.

Description of fruit:

mericarps irrigularly triangular, mat brown.

Propagules

Description of propagule:

seed, detached rhizomes or parts of rhizomes, detached parts of the stem.

Leaf

Description of leaf:

Oblong, serrate-denticulate, with 3-20 pairs of segments; in the lower part of the stem are the leaves longer than the internodes.

Phyllotaxy:

alternate no

opposite no

decussate no

whorled yes

Flower

Description of inflorescence:

Flowers in emergent, terminal spikes ( 3-35 cm), ± sessile, in whorls of 4 or 6 in the axis of lanceolate bracts (upper bracts simple, entire or serrate, bracts longer than flowers). Flowers with 2 minute bracteoles. Flowers in the upper part of the spike male, in the middle hermaphrodite and female in the lower part of the spike.